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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 11 |
| 5 | 28 |
| 6 | 66 |
| 7 | 152 |
| 8 | 339 |
| 9 | 748 |
| 10 | 1622 |
| 11 | 3496 |
| 12 | 7454 |
| 13 | 15832 |
| 14 | 33380 |
| 15 | 70192 |
| 16 | 146819 |
| 17 | 306508 |
| 18 | 637326 |
| 19 | 1323272 |
| 20 | 2738922 |
| 21 | 5662600 |
| 22 | 11677916 |
| 23 | 24061264 |
[0,0,1,4,11,28,66,152,339,748,1622,3496,7454, 15832,33380,70192,146819,306508,637326,1323272, 2738922,5662600,11677916,24061264] |